FIG. 1 is a schematic diagram of a Long Term Evolution (Long Term Evolution, LTE) radio access network (Radio Access Network, RAN) user plane (User Plane, UP) protocol stack in the prior art.
A packet data convergence protocol (Packet Data Convergence Protocol, PDCP) layer is mainly responsible for functions such as header compression, ciphering/deciphering, integrity protection, PDCP sequence number (Sequence Number, SN) maintenance, and in-sequence delivery.
A radio link control (Radio Link Control, RLC) layer is mainly responsible for functions such as data error detection, reordering, data concatenation, segmentation and re-segmentation, and duplicate detection by using an Automatic Repeat Request (Automatic Repeat reQuest, ARQ) mechanism.
A medium access control (Medium Access Control, MAC) layer is mainly responsible for functions such as mapping of logical channels to transport channels, a logical channel prioritization (Logical Channel Prioritization, LCP) procedure, error detection by using a hybrid automatic repeat request (Hybrid Automatic Repeat reQuest, HARQ) mechanism, and reporting of scheduling information.
With the continuous increase of mobile applications, many mobile services focusing on small packets emerge. For such small packets, the foregoing protocol architecture has the following problems:
In the existing architecture, for a data packet that enters an LTE RAN, first, a PDCP SN of 7 or 12 bits is added at the PDCP layer, and then after a PDCP protocol data unit (Protocol Data Unit, PDU) enters the RLC layer, concatenation or segmentation is performed, and in an unacknowledged mode (Unacknowledged Mode, UM), an RLC SN of 5 or 12 bits is further added to each RLC PDU, while in an acknowledged mode (Acknowledged Mode, AM), an RLC SN of 12 bits is further added to each RLC PDU. As a result, for a small packet, resource utilization is apparently reduced.